﻿#region LicenseHeader

// Copyright 2012 The Trustees of Indiana University.  All rights reserved.
// 
// The Indiana University licenses this file to you under the Apache License, 
// Version 2.0 (the "License"); you may not use this file except in compliance 
// with the License.  You may obtain a copy of the License at 
// 
// http://www.apache.org/licenses/LICENSE-2.0
// 
// Unless required by applicable law or agreed to in writing, software 
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
//  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  
// See the License for the specific language governing permissions and 
// limitations under the License.
// 
// @author Thilina Gunarathne (tgunarat@indiana.edu)

#endregion

#region

using System.Collections.Generic;
using AzureMRCore;
using AzureMRCore.DataTypes;
using AzureMRCore.MapRed;

#endregion

namespace KMeansMRSample
{
    internal class KmeansMapper :
        Mapper<IntKey, DoubleVectorValue, IntKey, DoubleVectorValue, IntKey, DoubleVectorValue>
    {
        protected override int Map(IntKey key, DoubleVectorValue value, List<KeyValuePair<IntKey, DoubleVectorValue>> dynamicData, IOutputCollector<IntKey, DoubleVectorValue> outputCollector, string programArgs)
        {
            var centroids = dynamicData;
            int numCentroids = dynamicData.Count;
            int vectorLength = value.Value.Length;

            double min = 0;
            int minCentroid = 0;
            for (int j = 0; j < numCentroids; j++)
            {
                double euDistance = 0;
                for (int i = 0; i < vectorLength; i++)
                {
                    euDistance += ((centroids[j].Value.Value[i] - value.Value[i])*
                                   (centroids[j].Value.Value[i] - value.Value[i]));
                }

                if (j == 0)
                {
                    min = euDistance;
                }
                else if (euDistance < min)
                {
                    min = euDistance;
                    minCentroid = j;
                }
            }

            outputCollector.Collect(IntKey.GetInstance(minCentroid), value);
            return 0;
        }
    }
}